1. Field of the Invention
The present invention relates to generally to optical systems and methods for detecting the presence of blood in fluids derived from the body. The present invention relates more specifically to a wound fluid blood detection device and method for use in conjunction with reduced pressure wound treatment (RPWT) systems and related systems. The detection device is operable to provide a notification signal to a health care provider and/or the patient of the presence of wound fluid with excess blood and/or is operable to modify or cease the reduced pressure wound treatment.
2. Description of the Related Art
General Background on Wound Treatment
Various therapies have been developed over time to facilitate the process of wound closure and healing. Wound closure generally involves the inward migration of epithelial and subcutaneous tissue adjacent the wound. This migration is ordinarily assisted by the inflammatory process, whereby blood flow is increased and various functional cell types are activated. Through the inflammatory process, blood flow through damaged or broken vessels is stopped by capillary level occlusion, where after cleanup and rebuilding operations may begin. Unfortunately, this process is hampered when a wound is large or has become infected. In such wounds, a zone of stasis (i.e. an area in which localized swelling of tissue restricts the flow of blood to the tissues) forms near the surface of the wound.
Without sufficient blood flow, the epithelial and subcutaneous tissues surrounding the wound not only receive diminished oxygen and nutrients, but are also less able to successfully fight bacterial infection and thus are less able to naturally close the wound. Until recently, such difficult wounds were addressed only through the use of sutures or staples. Although still widely practiced and often effective, such mechanical closure techniques suffer a major disadvantage in that they produce tension on the skin tissue adjacent the wound. In particular, the tensile force required in order to achieve closure using sutures or staples causes very high localized stresses at the suture or staple insertion point. These stresses commonly result in the rupture of the tissue at the insertion points, which can eventually cause wound dehiscence and additional tissue loss.
Additionally, some wounds harden and inflame to such a degree due to infection that closure by stapling or suturing is not feasible. Wounds not reparable by suturing or stapling often require prolonged hospitalization, with its attendant high cost, and major surgical procedures, such as grafts of surrounding tissues. Examples of wounds not readily treatable with staples or suturing include large, deep, open wounds; decubitus ulcers; ulcers resulting from chronic osteomyelitis; and partial thickness burns that subsequently develop into full thickness burns.
As a result of these and other shortcomings of mechanical closure devices, methods and apparatus for draining wounds by applying continuous reduced pressures have been developed. When applied over a sufficient area of the wound, such reduced pressures have been found to promote the migration of epithelial and subcutaneous tissues toward the wound. In practice, the application to a wound of reduced gauge pressure, commercialized by Applicant under a number of different reduced pressure wound treatment (RPWT) systems, typically involves the mechanical-like contraction of the wound with simultaneous removal of excess fluid. In this manner, RPWT augments the body's natural inflammatory process while alleviating many of the known intrinsic side effects, such as the production of edema caused by increased blood flow absent the necessary vascular structure for proper venous return.
Vacuum or reduced pressure induced healing of open wounds has recently been popularized by Kinetic Concepts, Inc. of San Antonio, Tex., through its commercially available RPWT systems product line. The reduced pressure induced healing process has been described in commonly assigned U.S. Pat. No. 4,969,880, issued on Nov. 13, 1990 to Zamierowski, as well as in its related patents, including U.S. Pat. No. 5,100,396, issued on Mar. 31, 1992;U.S. Pat. No. 5,261,893, issued on Nov. 16, 1993; and U.S. Pat. No. 5,527,293 issued Jun. 18, 1996, the disclosures of which are each incorporated herein by reference. Further improvements and modifications of the RPWT process are also described in U.S. Pat. No. 6,071,267, issued on Jun. 6, 2000 to Zamierowski and U.S. Pat. Nos. 5,636,643 and 5,645,081 issued to Argenta et al. on Jun. 10, 1997 and Jul. 8, 1997 respectively, the disclosures of which are each incorporated by reference as though fully set forth herein. Additional improvements have also been described in U.S. Pat. No. 6,142,982, issued on May 13, 1998 to Hunt, et al.
While RPWT has been highly successful in the promotion of wound closure, healing many wounds previously thought largely untreatable, some difficulties remain. Because the very nature of RPWT dictates an atmospherically sealed wound site, the therapy must often be performed to the exclusion of other beneficial and therefore desirable, wound treatment modalities and wound monitoring processes. Two such monitoring processes addressed in the present disclosure include wound fluid blood detection and blood gas monitoring. One such treatment modality addressed in the present disclosure is phototherapy—a method for wound treatment wherein appropriate wavelengths of light are directed into or about the wound bed.
Wound Fluid Blood Detection
Processes for analyzing the composition of fluids from the body are generally well developed in the art as long as the fluid may be removed as an in-vitro sample and analyzed remote from the patient. Various spectral absorption measurement techniques may be applied to body fluids to determine their composition and content. In particular, near infrared spectroscopy and optical detection have been used in the past in oximetry measurements associated with blood fluids. Colorimetric oximetry systems monitor the O2 saturation percentage in blood by comparing absorption in a red spectral band to absorption saturation at the isosbestic point of hemoglobin and deoxyhemoglobin and are typically employed in co-oximeters and cardiac bypass pump circuits. Photometric detection of hemoglobin has been accurately used for calculating the hematocrit levels at multiple (≧3) wavelengths at 570 nm, 640 nm and 805 nm typically in blood. These methods require removal of blood fluids from the body. Pulse oximetry methods allow for saturation measurements in-vivo but reliable hematocrit measurements have proven to be problematic due to scattering entities in whole anatomy such as skin and bone.
There are currently no devices, however, that perform real-time in-vivo blood detection monitoring, or blood detection in wound fluids as such fluids exist in direct association, or near direct association with the wound site Hematocrit and O2 saturation levels have been measured (Abbott's SaO2 PA catheter) in-vivo by optical scattering techniques and by colorimetry in whole free flowing blood. The presence of numerous optical components in the blood/wound-fluid mixture, however, generally limits the ability to use scattering based methods for real-time blood detection. Colorimetric based methods, on the other hand, do show some promise for application in conjunction with in-wound or near-wound fluid conduction systems as they are less susceptible to errors generated by non-blood opaque or dark fluid components. The specificity with which certain colorimetric techniques are able to discern the presence of blood in a mixed component fluid makes them, candidates for use in conjunction with in-vivo or near in-vivo detection.
It is therefore a primary object of the present invention to improve over the prior art by providing a system and method for detecting the presence of elevated levels of blood in body fluids in an in-vivo or near in-vivo environment.
It is a further object of the present invention to improve over the prior art by providing a system and method for detecting the presence of elevated levels of blood in wound fluids.
It is a further object of the present invention to improve over the prior art by providing a system and method for detecting the presence of elevated levels of blood in wound fluids while such fluids are present in the wound bed or immediately adjacent the wound bed subsequent to withdrawal from the wound.
It is a further object of the present invention to improve over the prior art by providing a system and method for detecting the presence of elevated levels of blood in wound fluids operable in conjunction with reduced pressure wound treatment systems.
It is a further object of the present invention to improve over the prior art by providing an additional safety feature for the operation of reduced pressure wound treatment systems through the detection of elevated levels of blood in wound fluids.
It is a further object of the present invention to improve over the prior art by providing a system and method for detecting blood in wound fluids in a manner sufficient to provide timely notification to a health care provider or the patient as to the existence of the elevated blood level condition.
It is a further object of the present invention to improve over the prior art by providing a system and method for detecting blood in wound fluids, operable in conjunction with a reduced pressure wound treatment system, and capable of providing timely modification or cessation of the reduced pressure wound treatment upon the detection and/or measurement of an elevated blood level condition.
It is still a further object of the present invention to provide a system and method for detecting the presence of blood in wound fluids without the need for additional invasive components being positioned within the wound bed or within the wound bed dressing.
It is still a further object of the present invention to provide a system and method for the detection of blood, in wound fluids operable in conjunction with a non-invasive blood gas monitoring device and a cooperative reduced pressure wound treatment system.
It is still a further object of the present invention to provide a system and method for the detection of blood in wound fluids operable in conjunction with a system for measuring wound dressing pressures and a cooperative reduced pressure wound treatment system.
It is still a further object of the present invention to provide a system and method for the detection of blood in wound fluids operable in conjunction with a reduced pressure wound treatment system, having functional components that additionally or alternately operate to provide phototherapy to the wound.
Finally, it is still a further object of the present invention to improve over the prior art by providing a method and apparatus for the detection of blood in wound fluids drawn into a reduced pressure wound treatment system that may be implemented in conjunction with the reduced pressure wound treatment system without the need for modification or interruption of the system.